1. Field of the Invention
The present invention relates to a device for changing the size of picture frames to be formed on photographic film by changing exposure aperture size, and also relates to a lens-fitted photographic film unit having such a device.
2. Related Art
Compact cameras having a picture frame size changing device are known, wherein either full size photography or panoramic photography may be practiced, and the field of view of the viewfinder is also changed to correspond to either the full size or the panoramic size photographic field.
In one of the known compact cameras having such a picture frame size changing device and an Albada-type inverted Galilean viewfinder, a reticule lens for displaying a panoramic field of view is provided in addition to a reticule lens for displaying a standard field of view having an aspect ratio for full size, and the panoramic reticule lens is removably insertable into the optical system of the viewfinder.
The conventional picture frame size changing devices mostly change the size of the exposure aperture between a full size of, for example, 24 mm .times.36 mm (aspect ratio 1.5) and a panoramic size of, for example, 13 mm .times.36 mm (aspect ratio 2.8) by using upper and lower masking plates.
On the other hand, lens-fitted photographic film units (hereinafter referred to as film units) are widely used, each of which has a simple exposure mechanism and contains a film cassette so that anyone may enjoy photographing with ease at low cost.
Because the film unit cannot be repeatedly loaded with film, after the exposure of all available frames of the contained film, the whole film unit is forwarded to a photofinisher. After the exposed film is removed to be processed for photo-printing, the empty housing of the film unit is returned to the manufacturer. The manufacturer disassembles and sorts out reusable parts of the film unit for recycling. It is desirable to reuse as many parts as possible without reprocessing, and to reassembled them into new film units. Also an exposure aperture size changing mechanism should be suitable for reuse, that is, it should be easy to assemble and disassembled, and should be suitable for automatic disassembly, inspection and reassembly.
These film units are also required to be as compact as possible. Therefore, the exposure aperture size change mechanism for a film unit should not much increase the size of the film unit.
In addition to this problem, the exposure aperture size change mechanism for a film unit should be inexpensive and easy to assemble, in keeping with the inexpensive nature of the film units.